Resistance to homologous and heterologous strains of potato virus Y in transgenic tobacco carrying the PVY^N coat protein gene

Abstract

. Resistance to homologous and heterologous strains of potato virus Y in transgenic tobacco carrying the PVY N coat protein gene. Can. J. Plant Sci. 77: 167-171. Pure breeding lines of transgenic Nicotiana tabacum L. 'Delgold' were generated which expressed transcripts of the coat protein gene of the tobacco veinal necrosis stain of potato virus Y (PVY N ) and were highly resistant to the virus. The form of resistance appeared to be RNA-mediated as no coat protein could be detected by enzyme linked immunosorbent assay. Resistant lines had two or three copies of the transgene but segregation analysis of the R 1 and R 2 progeny indicated that one copy in each line was functional for virus resistance. Simultaneous screening of lines for resistance against both PVY N and the heterologous PVY O (common) strain allowed for optimal selection of heterologous strain resistance. Resistance against the PVY-mn and PVY-nn strains and an ungrouped isolate, PVY-136, was less than against the PVY O isolate. The degree of heterologous strain resistance did not appear to directly correlate with the degree of sequence homology previously reported. The lines had no resistance against the related potato virus A and pepper mottle virus. Can. J. Soil Sci. 77: 167-171. On a obtenu des lignées généalogiques pures de tabac transgénique Nicotiana tabacum L. 'Delgold', exprimant les transcrits du gène de protéine capsidienne de la souche de la nécrose des nervures du tabac du PVY (PVY N ), mais manifestant une forte résistance au virus. Cette forme de résistance semble à médiation ARN, puisque aucune protéine capsidienne n'a pu être décelée par dosage immunoenzymatique. Les souches résistantes portaient deux ou trois copies du transgène, mais l'analyse de ségrégation des descendances R 1 et R 2 révélait qu'une copie de chaque souche conférait une résistance effective au virus. Des recherches simultanées de lignées dotées de résistance à la fois contre la souche homologue PVY N et contre la souche hétérologue PVY O (ordinaire) ouvraient la voie à une sélection optimale sur la résistance à la souche hétérologue. La résistance envers les souches PVY-mn et PVY-nn ainsi qu'envers un isolat non classifié, PVY-136, était moins forte que la résistance à la forme PVY O . Le degré de résistance à la souche hétérologue ne semble pas directement relié au degré d'homologie de séquence précédemment signalée. Les lignées ne démontraient pas de résistance au virus A de la pomme de terre ni au virus de la marbrure du piment, deux virus apparentés au PVY.

RNA Interference-Based Gene Silencing as an Efficient Tool for Functional Genomics in Hexaploid Bread Wheat

“…These results are in agreement with García-Pérez et al (2004), who reported that tobacco leaves of homozygous rootstocks have accumulated approximately double the amount of secondary siRNAs than the heterozygous rootstocks, suggesting that the induction of systemic silencing was strikingly dosage dependent. Similarly, several studies have suggested that transgene dosage can affect resistance of a transgenic line carrying transgenes homologous to viral sequences, because homozygous, but not hemizygous, R2 progenies were able to confer high level of resistance to different strains (Dinant et al, 1997;McDonald et al, 1997;Tenllado and Díaz-Ruíz, 1999;Tennant et al, 2001).…”

Influence of Coat Protein Transgene Copy Number on Resistance in Transgenic Line 63-1 against Papaya Ringspot Virus Isolates

“…The strengthening of the resistance phenotype and/or the broadening of the spectrum of resistance, as a consequence of increments in the number of transgene copies (and consequently the gene dosage), is a phenomenon already described. McDonald et al (1997) of PVY. In that report, a lower resistance was also seen against some heterologous strains, resembling the partial resistance to the Thai isolate described in this report.…”

Recovery Phenotype in PVYn—CP Transgenic Tobacco Cultivar

“…The resistance provided by expression of viral coat protein (CP) gene in transgenic plants ( 19) is a form of the pathogen-derived resistance (22). It was termed CPmediated resistance ( 1) and was reported for different plant viruses (1,8) Transgenic tobacco plants expressing PVY-CP were already shown to be resistant to that virus (7,12,17,26).…”